The distance a golf ball travels when struck by a golf club is determined in large part by club head speed at the point of impact with the golf ball. Club head speed in turn can be affected by the wind resistance or drag provided by the club head during the entirety of the swing, especially given the large club head size of a driver. The club head of a driver or a fairway wood in particular produces significant aerodynamic drag during its swing path. The drag produced by the club head leads to reduced club head speed and, therefore, reduced distance of travel of the golf ball after it has been struck.
Air flows in a direction opposite to the golf club head's trajectory over those surfaces of the golf club head that are roughly parallel to the direction of airflow. An important factor affecting drag is the behavior of the air flow's boundary layer. The “boundary layer” is a thin layer of air that lies very close to the surfaces of the golf club head during its motion. As the airflow moves over the surfaces, it encounters an increasing pressure. This increase in pressure is called an “adverse pressure gradient” because it causes the airflow to slow down and lose momentum. As the pressure continues to increase, the airflow continues to slow down until it reaches a speed of zero, at which point it separates from the surface. The air stream will hug the club head's surfaces until the loss of momentum in the airflow's boundary layer causes it to separate from the surface. The separation of the air streams from the surfaces results in a low pressure separation region behind the club head (i.e., at the trailing edge as defined relative to the direction of air flowing over the club head). This low pressure separation region creates pressure drag. The larger the separation region, the larger the pressure drag.
One way to reduce or minimize the size of the low pressure separation region is by providing a streamlined form that allows laminar flow to be maintained for as long as possible, thereby delaying or eliminating the separation of the laminar air stream from the club surface.
Reducing the drag of the club head at the point of impact (and, if possible, also prior to the moment of impact) would result in improved club head speed and increased distance of travel of the golf ball. When analyzing the swing of professional golfers, it has been noted that, although the heel/hosel area of the club head leads the swing during a significant portion of the downswing, the ball striking face leads the swing at (or immediately before) the point of impact with the golf ball. The phrase “leading the swing” is meant to describe that portion of the club head that faces the direction of swing trajectory. For purposes of discussion, the golf club and golf club head are considered to be at a 0° orientation when the ball striking face is leading the swing, i.e. at the point of impact. During the final portion of the downswing, the club head is traveling at its maximum speed, which may reach approximately 65 miles per hour (mph) to over 100 mph, and in the case of some professional golfers, to as high as 140 mph. It may be desirable to provide a golf club head with reduced drag when the speed of the club head is greatest.
Club heads that have been designed to reduce the drag of the head at the point of impact, or from the point of view of the club face leading the swing, may actually increase the drag during other phases of the swing cycle, such as when the heel/hosel region of the club head is leading the downswing. Thus, additionally, it may be desirable to provide a golf club head with reduced drag when the speed of the club head is greatest, while not having an increased drag during other portions of the golf swing.
It would be desirable to provide a golf club head that reduces or overcomes some or all of the difficulties inherent in prior known devices. Particular advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain embodiments.